Electric car battery maker A123 Systems has launched legal action against Apple, alleging that it had poached its engineers to build a large-scale battery division.
Analysts believe Apple is looking to design an electric car of its own.
A123 is a pioneering industrial lithium-ion battery maker, backed by a $249m (£169m) US federal grant. It filed for bankruptcy in 2012 and has been disposing assets.
Neither Apple nor A123 responded to requests for comment.